This invention relates to an apparatus for fitting an oil damper in a car, and particularly to an oil damper fitting apparatus provided with rubber bushings as buffers which contribute to make an automobile more comfortable to ride in.
Oil dampers are usually mounted between the frame and the axle of a car with the intervention of rubber bushings, which relieves shocks of generated breaking forces and serves as a free joint. There are two types of prior art rubber bushings, one being of compression-type to receive a load by compressive stress and the other being of shearing type to resist a load by shearing stress. The compression type rubber bushing is resistible to a large load but has disadvantages in that the stroke of deformation is relatively small for adequate buffer action. Further, the ability to interrupt the transmission of vibrations is insufficient. On the other hand, the shearing type rubber bushing has a good ability to interrupt vibrations and a relatively long stroke of deflection for buffer action. However, the shearing type rubber bushing has a defect in that the tolerable stress is too small to be utilized in such a space as voluminously restricted.
Passenger cars are usually provided between the frame and the axle with double acting oil dampers for the purpose of maintaining a rolling rigidity or a force resistible to inclination due to a centrifugal force generated during turning a side wind or the like. The damper has the respective damping forces in both the extensive and contractile directions of the piston rod. The breaking force in the extensive side is directed primarily to dampen vibrations above the spring and secondarily to suppress vibrations under the spring and hold the rolling rigidity. The breaking force in the compressive side is assigned for restraining the wheel from hopping up, breaking vibration under the spring and maintaining the rolling rigidity. Accordingly, the breaking force in the extensive side is remarkably greater than that in the contractile side, for example, the force in the extensive side being three or four times as large as the other in the case of 0.3 m/s piston speed. This suggests that an effective buffer should be mounted in the extensive side of the oil damper. When a soft rubber bushing is mounted in the compressive side of the oil damper, no breaking force will generate to dampen vibrations of small amplitudes, permitting vibrations in the tires. When the soft rubber bushings are provided on both sides of the oil damper, the car will have a poor rolling rigidity.
It is the primary object of this invention to provide an oil damper fitting apparatus free from the disadvantages as described above.
The apparatus according to this invention includes rubber bushings wherein a load is received initially by the shearing stress in the bushing compressed to the full stroke of deformation and by the compressive stress subsequently produced in the same. The rubber bushing in the extensive side is always stronger than that in the compressive side and initially contracted to half the stroke of shearing deformation when fitted. The rubber bushing in the contractile side is initially compressed to the substantially full stroke of shearing deflection to hold the rolling rigidity of a car.
In preferred embodiments, the rubber bushing is restrained from protruding in the both the outward and inward radial directions. Without being restrained from the outward protrusion, the rubber bushing under a heavy load would project outwardly to reduce the resisting force and make a wearing contact with the seat. Unless prevented from the inward deflection, it would have the inner periphery tightly contacted with the bolt portion of the oil damper and frictionally worn through their relative slide movement.
Other features, additional objects, and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the appending drawings.